University of Minnesota
University of Minnesota: Department of Mechanical Engineering

Human/Machine Laboratory

Contact: William K. Durfee
Mechanical Engineering 2101B
Telephone: (612) 625-0099

Graduate students work on the long-leg brace designed for individuals with spinal cord injury.








Creating computer-based visual, aural and haptic displays to
emulate a product and its interface.

Research Summary
Research in the Human/Machine Design (H/MD) Laboratory covers a wide range of topics related to the design and control of systems which interact with humans. Disciplinary areas include system dynamics and applied control, biomechanics and neuromuscular physiology of human movement, human-machine interactions, real-time digital control of dynamic systems, product design, product prototyping, and design education.

One major research thrust is the design and development of assistive technology systems to restore gait to individuals paralyzed as a result of spinal cord injury. Here, functional electrical stimulation (FES) is used to activate paralyzed muscle and thereby move the limbs. One thrust of this project is to develop practical products for use by those with spinal cord injuries. A system that combines FES with the controlled brake orthosis, a unique long-leg brace containing controllable friction brakes at the joints, is being refined and tested on subjects with spinal cord injury. Current efforts entail further development of the real-time controllers for the system and the design of a third generation device to meet the needs of its ultimate end-users.

In another project, mathematical models of the musculoskeletal system are being developed to aid in the design and control of assistive technology systems. Particular attention is being paid to creating efficient, nonlinear identification algorithms to customize the models for particular subjects. Several experimental protocols with both able-bodied and disabled human subjects are used to further improve the models. In addition to models, novel stimulation paradigms are being tested to reduce the premature fatigue in electrically stimulated muscle, and the electromyogram (EMG) is being analyzed for use as an indicator of muscle state for closed-loop control strategies.

A second major research thrust is to create better methods for engineers to prototype new designs. Prototyping tools based on virtual environment technology are being developed with a particular focus on haptic displays which enable the designer to reach out and "touch" the future product. Ongoing work in advanced servomechanism control is aimed at improving the technology of haptic interfaces, while human experimentation is used to understand the psychophysics of multi-modal virtual environments which combine visual, aural and haptic displays.